Unexplainable - Real-life zombies

Episode Date: October 1, 2025

Zombies might seem like the stuff of horror movies, but there are lots of examples of parasites taking over bugs’ bodies and bending them to their will. Guest: Mindy Weisberger, author of Rise of the Zombie Bugs: The Surprising Science of Parasitic Mind-Control For show transcripts, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unxtranscripts⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠For more, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unexplainable⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠And please email us! ⁠⁠⁠[e-mail]⁠⁠⁠We read every email.Support Unexplainable (and get ad-free episodes) by becoming a Vox Member today: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/members⁠⁠⁠⁠⁠⁠⁠⁠Thank you! Learn more about your ad choices. Visit podcastchoices.com/adchoices

Hey, I'm Matt Bouchelle, comedian, writer, and floating head you may or may not have seen on your FYP. And I'm starting a brand new podcast. Wait, don't swipe away. It's called, That Sounds Like a Lot. You know that feeling when you check your phone, read a few headlines and think, that sounds like a lot. I can't do this. Well, I can, and I'm going to get into it every Friday. You can watch on YouTube or listen wherever you get your podcast. I'm going to start by breaking down whatever insanity is happening in the world. And then I'll sit down with a comedian or actor or writer or, honestly, anyone who responds to my DMs. This is not the place to get the news, but it is a place to get the news.

to feel a little bit better about it. That sounds like a lot. Coming May 1st, part of the Vox Media Podcast Network. All right, so we're going to fade up on a moonlit field. You can see tall grasses moving in the breeze, a little bit of moonlight. And you can see on one of the blades of grass, there's an insect with its wings spread wide. This is Mindy Weisberger, a science writer. It looks like it might be a bee because it seems to be striped with bands of yellow and black.

But you get a little closer and you see that it is not a bee. It is in fact a fly. It is a dead fly. And the yellow bands that are striping its body are actually a fungus that has grown inside it and then burst through the seams in its exoskeleton. How did this fly become the star of a real-life horror movie? Well, several days ago, a spore from a fungus landed on it. And the spore burst.

buried inside of the fly and then started extending little filaments throughout its body, these fungal tendrils essentially that started digesting the fly from the inside out, consuming its fat cells. Now, the fly, as this was happening, behaved pretty normally, at least at first. But over the next few days, the fungus continued to grow, and it started congregating itself. first around the fly's heart, and then around what is the spinal cord in insects, and then around its brain. And then, after it had pretty much consumed most of the fat reserves in this fly, it was ready for the next stage, reproduction. So this is where the fly stops behaving like a fly and starts behaving like a fungus in a fly suit. It finds a place where it can climb.

And it's thought that getting to a higher position is better for the fungus because it produces these spores that are released in kind of an explosive poof. And the higher they are, the more widely they are likely to disperse. So the infected fly climbs up a blade of grass until it is literally no longer able to walk anymore. Again, stuffed with fungus. So at a certain point, stops walking. Extends its proboscis, which is a little trunk-like mouth part, and oozes out a sticky substance to basically glue it into place.

And then the fly dies. Its abdomen cracks open, and the spores come spilling out, ready to land on new flies and infect them. And to increase the odds that a fly will get spored, the fungus turns into a kind of. horrible fly fatale. These dead, fungus-striped flies with their big bloated abdomens

are very attractive to male flies who are looking to mate. Apparently, male flies of this species find big, swollen abdomens very alluring. And they also find this scent that the fungus starts to pump out this chemical signal alluring too, Like a sexy fungal love perfume.

That also sends a signal to male flies like, hey, you know, maybe here's something that you want to, you know, you want to hit that. I'm sorry. All of this draws in new victims, who, if everything works out, will soon be turned into their own fungal fly puppets. Mindy is a word for this kind of horror story. Zombification. She calls these flies, real-life zombies, and the fungus that takes them over is a real-life zombie fire. And it turns out there are a lot of examples of zombies and zombie fires out in nature.

There are so many, in fact, that Mindy wound up writing a whole book about them, called Rise of the Zombie Bugs. So this is unexplainable. I'm Bird Pinkerton. And today on the show, Mindy will tell us what we know and what we don't know about zombie bugs. Let's start by just defining some terms. What do we mean when we say, like, zombie fire or zombie? Sure.

So a zombie fire is an organism that manipulates the behavior of its host. And a zombie is a zombie is. an organism that is being manipulated to behave in a way that it normally would not, and which only benefits the parasite that's manipulating it. So to a certain extent, like, let's say you catch a cold. You're going to change your behavior because you're feeling sick. You feel like you need to rest more, you need to drink more water. These are all things that help you fight off the infection. So in a certain sense, that's the cold virus generating a change in. behavior, but it's a behavioral change that actually benefits you. For a zombie, the changes to its

behavior are not something that benefit the host. They only benefit the parasite. That's what makes it a zombie. So it'd be like if I got sick and instead of going into my room and trying to sleep it off, I went and I licked everybody that I could lick in order to spread the colds. Yeah, exactly. And so there are zomifying viruses. There are zomifying viruses. There are zonbifes. Zombefying fungi. There are insects that are able to zombify their hosts. There are worms that can zomify their hosts. So most of the organisms that they infect are arthropods. So bugs, but the colloquial version of bugs. Bugs. Exactly. I do have to apologize to entomologists because as far as entomologists are concerned, bugs are only insects with sucking mouth parts.

However, as we all know, colloquially, bugs covers a much broader range. Poor entomologists. Do you have personal favorite thombifiers or ones that make you squirm? Let's see. So hairworms infect terrestrial insects, but hairworms reproduce in water. And let's say a cricket is infected by. a hairworm. Now the worm grows inside this cricket. It grows to the point where it is many times the length of the cricket itself, like to the point where if you look at a cricket that is infected,

you might be able to see it moving around in the abdomen. This actually spoke to me because when I was pregnant, during the last month of my pregnancy, the fetus is getting really big at this point. So, you know, it's kind of like the movie Alien, right? Like you can see your foot. You can see an elbow. It's like, you know, there's something, there's something alive moving around inside your body. That is actually kind of what these infected crickets look like. But the worm has to get out eventually. So what it does is it manipulates the cricket's behavior to get it to find water and then jump in. And once it's in the water, the worm starts to emerge.

So watching a cricket trying to swim in a pool of water while this long thread-like worm is slowly over minutes, spooling out from its backside is something I highly recommend watching if, you know, you really want to squip yourself out. Oh my God, it's like, oh, sick. There are many, many videos of this on YouTube. That is so freaking nasty. This is so gross. Tyler's getting a change.

This is so gross. Oh, okay. But so there are all these different approaches, you're telling me. that fungi and viruses and insects used to do this zambifying. What are the sort of biggest categories of mysteries, I guess, about how they do this? Okay. Some of the biggest mysteries start with the moment that the host is infected, because obviously a body's first response to any kind of.

of infection is going to be an immune response. So the first thing that a zombie fire needs to do is to somehow get past that. And so that's a big, that's a big question is for zonbifiers from viruses to wasps to fungi to worms, when they get inside an organism where they're not supposed to be, how exactly are they telling their host immune system? Now, there's nothing to see here. You can just go about your business. You don't need to worry about me. So that's mystery number one. Yeah, that's a big one. Then, of course, another one is once it gets to the point of manipulation, first of all, what are the cues? How does it decide, okay, now is the right time to, you know, to get this house move into a place where I need to be? So the description that I gave you earlier of the

the fly in a moonlit field, there seems to be a circadian rhythm element to, you know, the fungus that infects flies specifically because they start their climbing at night. Got it. So mystery number two would basically be, are there things out in the environment that trigger a fungal takeover? And how does the zombie fire kind of recognize those cues, I guess, it sounds like. Yeah. And the third big question is obviously the nuts and bolts of how is it manipulating behavior. Right. The thing about this field is that there is still so much that scientists are piecing together about the precise mechanisms of how this works. Behavior is something that is just super complicated, even in insects.

So when we look at, for example, the wasp, the parasitizes, orb weaving spiders, scientists have found that in the spiders that are zomified, what the wasp does, it lays an egg on the spider. The egg hatches and the wasp larvae, essentially piggybacks on the spider and drinks from it, like it's a living juice box. And the spider just goes about its business until the larva is ready to reproduce. And then somehow the wasp larvae is manipulating the spider

to think that it's time to molt so that the spider makes a different type of web than it normally does. Something called a resting web. It's reinforced and it's meant to support the spider and protect the spider while it's molting. And then once that web is dead, done, the wasp larvae drains the spider dry, the spider's empty husk of a corpse drops to the

ground, and the wasp larvae builds its cocoon and sets itself up in the spider's final web to hang out until it becomes an adult wasp. So basically, the spider is convinced by this, this wasp larvae in some way to build a cocoon for it. It uses all of its final webbery to, like, build a really nice little house for the wasp to grow up in. I like final webery. Yeah. So what scientists found is that when spiders start making that final web, their little spider brains are being flooded with ectosteroids, which is the hormone that the spider naturally releases when it's ready to build a molting web. So it's actually, it's almost like it's taking a page out of the spiders existing biochemistry. And scientists aren't sure yet if what the wasp larva is doing is,

like, is the larvae actually producing the ectosteroid? Is it somehow triggering its production in the spider through another compound? That's something that they're still figuring out. But clearly, it's something that is already sort of baked into the spider's biology, that this is, this is a chemical trigger that lets it know, now it's time to build this kind of web, except this time it's not going to survive the process. So it is sort of a like, you couldn't necessarily get the spider to do something that it wouldn't be able to do under any other circumstances, but you can like puppet it to do things that it might do otherwise. That seems to be the much more common strategy among zombie fires, but exactly how they're being activated is still a question.

Why is it important to understand sort of more about how this behavior manipulation works? Yeah, that's a really good question. And it is one that we will answer after the break. It's all about you. And when you fly with Virgin Atlantic in their upper class cabin, they take the VIP treatment to the next level. With a private wing to check in and your own security channel at London Heathrow, you can glide from your car to their clubhouse. a destination in its own right in 10 minutes or less.

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Follow Pretty Tough wherever you get your podcasts. I'm a Stead Herndon, and this is America, actually. We're all talking to each other to see, what did we do wrong? What do we not see? I'm in Washington, D.C. this week to interview Ruben Gallego. He's a Democratic senator from Arizona, and he's been thinking openly about running for higher office. But he's recently running to some hot water because of his connection to Congressman Eric Swalwell. I have to learn from this, and I will learn from this.

But for me, it's not a 2028 question. It's about what it means to be a better first boss in my office and also a better senator to my constituents. This week on America, actually, we asked Gallego about predatory behavior in Washington, his plans for immigration reform, and more. Scientists still have a lot of questions about the precise mechanics of zombification. But if they could learn more about how zombifiers take over their victims, it turns out they could learn a lot that might benefit all of us. this in a lot of ways is looking at really big questions about how behavior works, which is something that is, like scientists are still piecing this together on so many levels for all different types of organisms because there are so many factors that shape behavior.

Some of them are genetics. Some of them are biochemical. Some of them have to do with environments. Some of them have to do with social relationships. So this is one way of trying to understand behavior writ large. You mentioned that these insects suppress the immune systems of their hosts. Is there stuff that we could learn from that about, like, how immune systems work in general? Oh, yeah.

Looking at the immunosuppressive aspect of zombifiers is definitely something that is a huge area of interest because that could inform the development of immunosuppressive drugs, which is just something that would be hugely beneficial to people. Right. Not that this should be all about what's in it for me, but that is usually a consideration for scientific research. Could there potentially be applications for this that have medical applications? And so there is not yet a direct line between any research into how Zobifiers evade their host's immune system and the development of some kind of pharmaceutical immunosuppressive, but that's definitely something that is part of the mix

when scientists are following that line of investigation. I think about all the insects that invade Holmes, some of which are beneficial, some of which are less so. Could we potentially borrow from this to, like, fight off pests? Pest control is definitely one avenue that, that scientists have explored as a way of, okay, well, you know, is there some way that we can take what we're seeing these zombie fires do to insects and apply it to insects that we don't like?

So baccular viruses, which are these viruses that infect caterpillars and make them climb and then dissolve their bodies into goo, this is something that has been deployed as a strategy for pest control in China and in Europe, in the U.S., in Brazil. So these types of viruses, they're an interesting alternative to traditional insecticides because they are very targeted. They are less toxic to the environment. They're not harmful to insects that are not their host species, and they're not toxic to people. But they're not as quick as I think the insecticides that people have gotten used to, and people like things to be quick and they like them to be absolute. So what seems like is the best way is perhaps to incorporate this alongside insecticides

and use this along with other approaches because there are a lot of benefits to just, you know, going full-on zombie warfare to get rid of our agricultural pests. Is there any attempt to like design our own to be like, all right, we really want to get rid of American cockroaches? You are describing the plot of a zombie movie right now where a team of scientists are working with, they're studying zombie bugs, and they're like, oh, hey, wouldn't it be great if we could manufacture an artificial version of this zombie virus and release it into the wild? What could possibly go wrong? Oh, no, the hubris. Well, this does kind of get to a question that I have around all of this, which is maybe a silly question, but like, could humans be zombieified this way? Are we also susceptible to this? Well, there are some types of pathogens that are

known to manipulate behavior in mammals and indeed in humans too. So rabies, of course, has been around and has been, there have been medical cases of rabies-infected humans that are thousands of years old with documentation of the heightened aggression. So, So there is already a virus among us that can manipulate human behavior. And recently there have been studies into toxoplasma Gandhi, which is the pathogen that causes toxoplasmosis. So this is an organism that its definitive host is cats. So it's very entrenched amongst human populations. and in fact, many, many people, millions of people carry taxoplasma Gandhi, but it doesn't cause

any symptoms. It tends to be dangerous in people that are pregnant or in immunocompromised people. Most of the people who are carrying taxoplasma Gandhi have no symptoms. However, there have been studies recently in the last 10, 15 years or so, that have looked at people who are carrying the parasite and have found that they have found that they have been studies recently, like, in the last 10, there does seem to be evidence of certain types of behavior, of being more risk-taking, of being bolder, in some groups of women being more nurturing.

And what's interesting about it is that Toxoplasma Gandhi is known for manipulating behavior in rodents. And what it does is it makes them bolder and less afraid of cats, because Toxoplasma Gandhi needs to reproduce. juice inside cats. So it infects rodents, and then to get back into a cat, it makes the rodent less afraid of and attracted to the smell of cat pee. And that brings the rodent closer to a cat than it would normally go, and then once it's eaten, then the parasite is back inside the cat. And scientists have found that this is true for other animals too. So hyena cubs that are infected with Toxoplasma Gandhi are bolder around lions and are more likely to be eaten by lions.

Chimpanzees that are infected with toxoplasma Gandhi lose their fear of jaguars. And some studies found that people who are infected with Toxoplasma Gandhi are more likely to make risky business decisions or be bolder in traffic. So there's still a lot of work to be done because obviously human behavior is its own form of complicated. But there is some evidence that seems to suggest that toxoplasm, Gandhi can shape human behavior too. What?

Do I just blow your mind? Yes. That's so... I can send you links to the studies. I think I was expecting you to be like, no, unless you have rabies, you're definitely not. Well, do you have a cat? No, I don't. I have to.

So there could literally at this moment be zombie fires within us. shaping us in some way? It's entirely possible. But there are so many things that make us who we are, that shape how we behave, there are environmental factors, there are social factors.

The responsible answer. Oh, sure, but there might also be zonifiers. In a world where a team of scientists, they're working with, they're studying zombie bugs, and they're like, Oh, hey, wouldn't it be great if we could manufacture an artificial version of this zombie virus

and release it into the wild? What could possibly go wrong? Everything goes wrong. Kill them. Kill the cockroaches. You can't kill a cockroach if it's already undead. Guys, I think Gregor might have just turned into a cockroach. Coming soon, under the kitchen,

sink near you. There are so many more weird, wonderful zombie stories in Mindy Wiseberger's book. That is Rise of the Zombie Bugs. So if you want to read about zomified cicadas or fungi that will remind you of the show The Last of Us or any number of other skin crawling, mildly horrifying things, please check it out. This episode was produced by me, Bird Pinkerton. It was edited by Sarah K. K. Kramer. Meredith Hodnott runs our show. Noam Hassemfeld makes the music. Christian Ayala did the spooky sound design and the mixing on this episode. Melissa Hirsch did not enjoy all the gross bug stuff, but she powered through and check the facts anyway. Thanks, Melissa. And the fact is that Julia Longoria and Jorge Just are just lovely human beings. Thanks to Brian Resnick, always, for co-creating the show. Thanks to Jonah for helping. Thanks to Charlie Harding, Claire White, Sergio Scardino, and Angela Chen for their

voice work. And thanks to you for listening. If you have thoughts about this episode, we are at Unexplainable at Vox.com. I love hearing from you all, so please email us. If you want to support the show and help us keep making it, please join our membership program. It is at Vox.com slash members and you'll get ad-free podcasts, unlimited access to Vox journalism. And if you tell our bosses that you signed up because you loved Unexplainable, it goes a long way. So that is at Vox.com slash members. You can also support us by leaving a nice rating, perhaps, or a review, or just by telling people in your life to listen. But Unexplainable is part of the Vox Media Podcast Network, and we will be back in your feed next week.